The field of the invention is computer terminal equipment, and particularly, display terminals suitable for industrial applications.
Computer terminals are commercially available in a wide variety of configurations. The most common configuration includes a cathode ray tube display (CRT) and a keyboard which may either be attached to the display or contained in a separate housing that is electrically connected to the display. Such CRT terminals also include one or more serial communications ports which may be connected to a similar port on another piece of equipment such as a computer, process controller, or programmable controller.
Although the CRT display is very general purpose, the same cannot be said of the keyboard. For many commercial applications a typewriter keyboard is appropriate, but there are many instances in industrial applications where special purpose mnemonics, symbols or fonts are used and in which a standard alpha-numeric keyboard becomes awkward. One such application, for example, is the input of control program data into a programmable controller.
Filed on even date herewith is a copending U.S. patent application entitled "Industrial Terminal" in which the circuitry is described for a multi-purpose terminal. Circuitry for driving the CRT display and receiving data at serial I/O ports is provided on a main circuit board. This portion of the circuitry is very general purpose in nature and separate circuitry for "tailoring" the terminal to a specific application is provided on a separate application module. The application module also includes the data entry apparatus peculiar to that application, which in most instances is a keyboard with suitable symbols.